A queue with a capacity of zero is clearly not a valid virtio queue.
Some emulators report zero queue size if queried with an invalid queue
index. Instead of crashing in this case let us just return -EINVAL. To
make that work properly, let us fix the notifier cleanup logic as well.
Signed-off-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
---
This patch is motivated by commit 86a5597 "virtio-balloon:
VIRTIO_BALLOON_F_FREE_PAGE_HINT" (Wei Wang, 2018-08-27) which triggered
the described scenario. The emulator in question is the current QEMU.
The problem we run into is the underflow in the following loop
in __vring_new_virtqueue():
for (i = 0; i < vring.num-1; i++)
vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1)
Namely vring.num is an unsigned int.
RFC --> v1:
* Change error code from -EINVAL to -ENOENT, so we are in line with the
other transports.
* Push down the detection of the error into virtio_ccw_read_vq_conf().
---
drivers/s390/virtio/virtio_ccw.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index fc9dbad476c0..2c6f8a5009ed 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -272,6 +272,8 @@ static void virtio_ccw_drop_indicators(struct virtio_ccw_device *vcdev)
{
struct virtio_ccw_vq_info *info;
+ if (!vcdev->airq_info)
+ return;
list_for_each_entry(info, &vcdev->virtqueues, node)
drop_airq_indicator(info->vq, vcdev->airq_info);
}
@@ -413,7 +415,7 @@ static int virtio_ccw_read_vq_conf(struct virtio_ccw_device *vcdev,
ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_VQ_CONF);
if (ret)
return ret;
- return vcdev->config_block->num;
+ return vcdev->config_block->num ?: -ENOENT;
}
static void virtio_ccw_del_vq(struct virtqueue *vq, struct ccw1 *ccw)
--
2.16.4
